Gmirror - how to do?

[Paul Mather]

On Sat, 2005-02-05 at 17:33 -0600, Karl Denninger wrote:
> On Sun, Feb 06, 2005 at 12:08:42AM +0100, Pawel Jakub Dawidek wrote:
> > On Sat, Feb 05, 2005 at 05:04:15PM -0600, Karl Denninger wrote:
> > +> > Remember not to boot the main machine with this disk inside, as it can
> > +> > be tasted before your main 'boot' mirror. Inserting this disk after
> > +> > boot, when your 'boot' mirror is configured should be safe.
> > +> 
> > +> Nope, won't work.
> > +> 
> > +> The mirrors potentially have different PHYSICAL slice sizes (remember
> > +> this debate a while back on this list?) and if I do this, I'm guaranteed to
> > +> screw the partition table, as the fdisk size of the slice table will be
> > +> picked up.
> > 
> > Sorry, but I don't understand.
> > How can you touch slices configuration by labeling ad4s1?
> > 
> > -- 
> > Pawel Jakub Dawidek                       http://www.wheel.pl
> > pjd at FreeBSD.org                           http://www.FreeBSD.org
> > FreeBSD committer                         Am I Evil? Yes, I Am!
> 
> 
> Won't the gmirror system create the new mirror (on the "backup disk" using 
> the full size of the slice?

Gmirror will truncate the mirror's size to that of the smallest mirror
component at creation (or, if you try and insert a provider that is too
small for an existing mirror, it will [should] refuse to add it).  So,
if you create a slice within the mirror component (/dev/mirror/...) then
it cannot, by definition, be "too big."  The slice may not cover the
entire drive, but it won't be bigger than the drive.

The only problem you can run into is if you try and use a drive that is
smaller than the smallest one used to create the initial mirror.  That
will not work.

Cheers,

Paul.
-- 
e-mail: paul at gromit.dlib.vt.edu

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